In a stapler which is arranged to bend legs of a staple penetrated through sheets of paper to be bound along a rear surface of the sheets of paper thereby to bind the sheets of paper, a staple driving portion for striking out the staple toward the sheets of paper is disposed on one side of a feeding path of the sheets of paper, and a clincher device for bending the legs of the staple penetrating through the sheets of paper and protruding to the rear surface side of the sheets of paper along the rear surface of the sheets of paper is disposed on the other side of the feeding path so as to oppose to the staple driving portion across the feeding path. In the general clincher device for the stapler having been known conventionally, a fixed clincher, provided at an upper end surface with guide grooves for bending and guiding a pair of the legs of the staple toward the inside, is disposed on a rear surface side of the sheets of paper. The pair of the legs of the staple struck out toward the sheets of paper from a front surface side of the sheets of paper by the driving portion are protruded to a rear surface side of the sheets of paper and engage with the guide grooves, whereby the legs are bent and guided toward the inside.
In the aforesaid fixed clincher, a staple is struck toward the sheets of paper by a driver plate provided at the staple driving portion. The legs of the staple, which penetrate the sheets of paper and protrude to the rear surface side of the sheets of paper, engage with the guide grooves and are bent and guided toward the inside. The staple is formed at a base portion of each of the legs thereof with curved loops so that the tip ends of the legs of the staple abut against the rear surface of the sheets of paper thereby to complete the staple binding. According to the staple binding using such the fixed clincher, since the height of the loop formed at the base portion of each of the legs of a staple is quite large as compared with a thickness of the sheet of paper, the thickness of the bound portion by the staple becomes large. Thus, when plural sets of bound papers are stacked, the plural sets of bound papers incline.
JP-A-10-128682 discloses an electric stapler including a clincher device provided with movable clinchers which respectively operate to engage with the legs of the staple, which penetrate the sheets of paper and protrude to the lower surface side of the sheets of paper, and to bend the legs of the staple from the base portion sides thereof. According to such the clincher device, a pair of the movable clinchers are disposed on the lower surface side of the sheets of paper, and after almost the entire portions of the legs of the staple penetrate the sheets of paper, the movable clinchers are operated thereby to bend the legs of the staple from the base portions thereof along the rear surface of the sheets of paper. When such the movable clinchers are employed, the loops formed at the both ends of a staple can be eliminated or the height of the loops can be made small. Thus, since the bound shape of the staple can be made flat, such a phenomenon can be prevented from occurring that when plural sets of bound papers are stacked, the plural sets of bound papers incline.
However, in this clincher device using the movable clinchers according to the related art, a driving mechanism for operating the movable clinchers is needed. In the electric stapler arranged so as to strike the staple by the electric motor, the movable clinchers are operated at a suitable timing after the staple penetrates the sheets of paper by a driver driven by the electric motor. Thus, a related driving mechanism such as a cum and a link for driving the movable clinchers by the electric motor for driving the driver is required, which results in an increase of a cost of the electric stapler. Further, in the electric stapler in which the staple driving portion and the clincher device are separately disposed at the both sides of the feeding path so as to oppose to each other across the feeding path, it is necessary to provide a driving source such as another electric motor for driving the clincher device, which results in the further increase of the cost.